Wideband active small antenna design using the dummy antenna for T-DMB system

The frequency band for T-DMB (terrestrial digital multimedia broadcasting) system in Korea is assigned to the VHF channel 7~13 (174 MHz~216 MHz) and channel 8 and channel 12 are used in Seoul. The length of the lambda/4 monopole with an infinite ground is about 38 cm to make a resonance at 200 MHz. Generally, meander line, high dielectric constant material and parasitic elements have been used to reduce the large size of a T-DMB antenna. But, as the effective size of an antenna is reduced, the bandwidth is getting narrower. So, these passive small antennas can not cover the wideband of T-DMB. In this work, the wideband active small antenna is proposed. We integrated the lambda/32 (4.75 cm) short monopole with LNA (low noise amplifier) for the mobile application. To obtain the wideband characteristic, we used the dummy antenna, which is the 2-port equivalent circuit of real antenna.